Gneiss missing first parameter

There is a very similar question here.

If you are trying to fit a linear model with D categories, you will need to figure out a way to encode that model with D-1 contrasts. As a default, the first category is chosen as the reference contrast. We are using patsy to extract these design matrices, so it may be worthwhile to read the patsy documentation to figure out how to properly encode the formulas.

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